The breakdown voltage, one of the characteristics of a semiconductor power device, is designed towards targets of having a minimal conduction resistance, a low reverse leakage current and a fast switching speed, so as to reduce a conduction loss as well as switching loss. Having a wide bandgap (Eg=3.26 eV), a high threshold breakdown strength (2.2 MV/cm) and a high thermal conductivity (4.9 W/cm-K), silicon carbide (SiC) is regarded as an ideal material for power switching devices. Therefore, many associated industrialist are dedicated in the development and research of silicon carbide power devices.
For example, the U.S. patent publication No. US2013/0161736 discloses a trench metal oxide semiconductor transistor device and manufacturing method thereof The trench metal includes a substrate of a first conductivity type, a drift region of the first conductivity type, a deep trench doped region of a second conductivity type, an epitaxial region of the second conductivity type, a trench gate, a gate insulating layer, a source region, a drain electrode and a source electrode. The drift region in the first conductivity type has at least one deep trench therein, and the deep trench doped region of the second conductivity type is disposed in the deep trench. The trench gate passes through the epitaxial region of the second conductivity type, and a distance between a bottom of the trench gate and a bottom of the deep trench doped region of the second conductivity type is 0.5 um to 3 um. Accordingly, when the trench metal oxide semiconductor transistor device is operated with a reversed withstand voltage, power line distribution is effectively dispersed to further enhance the reliability of the device.
However, in the above trench metal oxide semiconductor transistor device, a depth of the deep trench doped region of the second type is limited by an energy of ion implantation and a thickness of a hard mask layer. In general, an ion implantation apparatus having a large energy and thus capable of implanting ion implantation exceeding a depth of 2 um in one operation is quite rare. Thus, the development and voltage withstanding capability of the trench metal oxide semiconductor transistor device need to be further improved.